/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.tribes.group;

import java.util.Arrays;
import java.util.Comparator;

import org.apache.catalina.tribes.Member;

/**
 * <p>
 * Title: Membership - Absolute Order
 * </p>
 * 
 * <p>
 * Description: A simple, yet agreeable and efficient way of ordering members
 * </p>
 * <p>
 * Ordering members can serve as a basis for electing a leader or coordinating
 * efforts.<br>
 * This is stinky simple, it works on the basis of the <code>Member</code>
 * interface and orders members in the following format:
 * 
 * <ol>
 * <li>IP comparison - byte by byte, lower byte higher rank</li>
 * <li>IPv4 addresses rank higher than IPv6, ie the lesser number of bytes, the
 * higher rank</li>
 * <li>Port comparison - lower port, higher rank</li>
 * <li>UniqueId comparison- byte by byte, lower byte higher rank</li>
 * </ol>
 * 
 * </p>
 * 
 * @author Filip Hanik
 * @version 1.0
 * @see org.apache.catalina.tribes.Member
 */
public class AbsoluteOrder {
	public static final AbsoluteComparator comp = new AbsoluteComparator();

	protected AbsoluteOrder() {
		super();
	}

	public static void absoluteOrder(Member[] members) {
		if (members == null || members.length == 0)
			return;
		Arrays.sort(members, comp);
	}

	public static class AbsoluteComparator implements Comparator {
		public int compare(Object o1, Object o2) {
			if (!((o1 instanceof Member) && (o2 instanceof Member)))
				return 0;
			return compareMembers((Member) o1, (Member) o2);
		}

		public int compareMembers(Member m1, Member m2) {
			int result = compareIps(m1, m2);
			if (result == 0)
				result = comparePorts(m1, m2);
			if (result == 0)
				result = compareIds(m1, m2);
			return result;
		}

		public int compareIps(Member m1, Member m2) {
			return compareBytes(m1.getHost(), m2.getHost());
		}

		public int comparePorts(Member m1, Member m2) {
			return compareInts(m1.getPort(), m2.getPort());
		}

		public int compareIds(Member m1, Member m2) {
			return compareBytes(m1.getUniqueId(), m2.getUniqueId());
		}

		protected int compareBytes(byte[] d1, byte[] d2) {
			int result = 0;
			if (d1.length == d2.length) {
				for (int i = 0; (result == 0) && (i < d1.length); i++) {
					result = compareBytes(d1[i], d2[i]);
				}
			} else if (d1.length < d2.length) {
				result = -1;
			} else {
				result = 1;
			}
			return result;
		}

		protected int compareBytes(byte b1, byte b2) {
			return compareInts((int) b1, (int) b2);
		}

		protected int compareInts(int b1, int b2) {
			int result = 0;
			if (b1 == b2) {

			} else if (b1 < b2) {
				result = -1;
			} else {
				result = 1;
			}
			return result;
		}
	}

}
